1. Field of the Invention
The present invention relates to a diaphragm and an accumulator containing the same which is used for hydraulic systems and the like of automobile vehicles, industrial vehicles and the like.
2. Description of the Prior Art
An accumulator has a pressure accumulating function and generally comprises a metallic shell and a diaphragm installed within the shell for separating the internal space of the shell into two chambers (a gas chamber and an oil chamber) The accumulator contains a gas such as nitrogen sealed in the gas chamber and also includes communication of the oil chamber with a hydraulic circuit of the hydraulic system via a circulation hole. When pressure in the oil chamber becomes larger than that of the gas chamber by hydraulic oil flowing into the oil chamber via the circulation hole, the diaphragm elastically deforms so that the gas within the gas chamber is compressed and the volume of the gas chamber become smaller. On the other hand, when the oil chamber is enlarged, pressure is accumulated in the hydraulic oil. The diaphragm generally comprises a resin layer for gas shielding, a rubber layer adjacent to the gas chamber formed on the resin layer, and a rubber layer adjacent to the oil chamber formed on the resin layer, wherein these two rubber layers sandwich the resin layer. As a material for forming both of the rubber layers adjacent to the gas chamber and the oil chamber, butyl rubber is used.
However, if a diaphragm having the above construction is subjected to an operating durability (test) at a temperature of not more than room temperature and under high operating pressure, the rubber is repetitively compressed and strained by elastic deformation. Thus, the rubber is rubbed and worn, resulting in cracking on the rubber layers and deterioration in durability for the diaphragm. Therefore, there is a problem such that service life of an accumulator using such a diaphragm is shortened.
In view of the foregoing, it is an object of the present invention to provide a diaphragm having good operativity both at a low temperature and room temperature and also having superior durability, and further to provide an accumulator using the same.